English names: Karnal bunt of wheat
Nordic names: Indisk stinkbrand (DK)
Major host plants
The main host of T. indica is wheat (Triticum spp.), but it has also been found on Triticale. Rye (Secale spp.) is expected to be a host too.
Symptoms depend on the climate and are most clear when humid conditions prevail at flowering. Infection causes a reduction in the length of ears as well as in the number of spikelets of the bunted ears, and the plants may be dwarfed. In general, only a few spikelets per ear are infected and the affected grains are not swollen. Finally, dusty, brown to black spore masses will develop in the grains. Spores have a characteristic smell like decaying fish (trimethylamine) as do those of T. tritici, T. foetida and T. controversa.
The disease has spread from India to other parts of Asia and to Mexico and North America.
A map can be downloaded from EPPO's website. See instructions here.
T. indica survives more than 4 years in the soil. At temperatures between 20 and 25°C teliospores will germinate in the soil around the time of flowering of the wheat crop. The teliospores produce a promycelium bearing many primary sporidia, and these give rise to secondary sporidia. Both types of sporidia are dispersed by wind or rain splash to the wheat ears. High humidity associated with light rain showers and cloudy weather is most favourable for infection of the ears at flowering.
Spores can be spread by wind over long distances, but infested seed is the main means of international spread.
Detection and inspection
Samples of seed should be tested by relevant test methods in laboratory. Visual inspection is not sufficient, since low levels might pass undetected. Only laboratory methods can distinguish between the different bunt diseases.
If a field crop is suspected to be infected, the crop should be inspected during the period between heading and harvest. Any bunted seeds found during field inspection should be examined in the laboratory.
Pest status and importance
The disease is nearly impossible to eradicate once introduced. An EU evaluation of the costs for the region, as a consequence of an introduction and spread, indicated very high yearly costs.
Source of information
See further information here
Author: Göran Kroeker
Editor: Dorthe Vestergaard